<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
    <title>DbEnv::lock_detect()</title>
    <link rel="stylesheet" href="apiReference.css" type="text/css" />
    <meta name="generator" content="DocBook XSL Stylesheets V1.73.2" />
    <link rel="start" href="index.html" title="Berkeley DB C++ API Reference" />
    <link rel="up" href="lock.html" title="Chapter 7.  The DbLock Handle" />
    <link rel="prev" href="envset_lk_tablesize.html" title="DbEnv::set_lk_tablesize()" />
    <link rel="next" href="lockget.html" title="DbEnv::lock_get()" />
  </head>
  <body>
    <div xmlns="" class="navheader">
      <div class="libver">
        <p>Library Version 11.2.5.3</p>
      </div>
      <table width="100%" summary="Navigation header">
        <tr>
          <th colspan="3" align="center">DbEnv::lock_detect()</th>
        </tr>
        <tr>
          <td width="20%" align="left"><a accesskey="p" href="envset_lk_tablesize.html">Prev</a> </td>
          <th width="60%" align="center">Chapter 7. 
                The DbLock Handle
        </th>
          <td width="20%" align="right"> <a accesskey="n" href="lockget.html">Next</a></td>
        </tr>
      </table>
      <hr />
    </div>
    <div class="sect1" lang="en" xml:lang="en">
      <div class="titlepage">
        <div>
          <div>
            <h2 class="title" style="clear: both"><a id="lockdetect"></a>DbEnv::lock_detect()</h2>
          </div>
        </div>
      </div>
      <pre class="programlisting">#include &lt;db_cxx.h&gt;
 
int
DbEnv::lock_detect(u_int32_t flags, u_int32_t atype, int *rejected);</pre>
      <p>
         The <code class="methodname">DbEnv::lock_detect()</code> method runs one iteration of the deadlock
         detector. The deadlock detector traverses the lock table and marks one
         of the participating lock requesters for rejection in each deadlock it
         finds.
    </p>
      <p>
         The <code class="methodname">DbEnv::lock_detect()</code> <span>
            
            <span>
                method either returns a non-zero error value or throws an
                exception that encapsulates a non-zero error value on
                failure, and returns 0 on success.
            </span>
        </span>
    </p>
      <div class="sect2" lang="en" xml:lang="en">
        <div class="titlepage">
          <div>
            <div>
              <h3 class="title"><a id="idp8032192"></a>Parameters</h3>
            </div>
          </div>
        </div>
        <div class="sect3" lang="en" xml:lang="en">
          <div class="titlepage">
            <div>
              <div>
                <h4 class="title"><a id="idp8032040"></a>flags</h4>
              </div>
            </div>
          </div>
          <p>
                          The <span class="bold"><strong>flags</strong></span> parameter is currently
                          unused, and must be set to 0.
                     </p>
        </div>
        <div class="sect3" lang="en" xml:lang="en">
          <div class="titlepage">
            <div>
              <div>
                <h4 class="title"><a id="idp8024496"></a>atype</h4>
              </div>
            </div>
          </div>
          <p>
                          The <span class="bold"><strong>atype</strong></span> parameter specifies which
                          lock request(s) to reject. The deadlock detector will reject the lock
			  request with the lowest priority.  If multiple lock requests have the
			  lowest priority, then the <span class="bold"><strong>atype</strong></span>
			  parameter is used to select which of those lock requests to reject.
			  It must be set to one of the following list:
                     </p>
          <div class="itemizedlist">
            <ul type="disc">
              <li>
                <p><a id="detect_DB_LOCK_DEFAULT"></a>
                  <code class="literal">DB_LOCK_DEFAULT</code>
            </p>
                <p>
		 Use the default lock policy, which is DB_LOCK_RANDOM.
            </p>
              </li>
              <li>
                <p><a id="detect_DB_LOCK_EXPIRE"></a>
                  <code class="literal">DB_LOCK_EXPIRE</code>
            </p>
                <p>
                 Reject lock requests which have timed out.  No other deadlock
                 detection is performed.
            </p>
              </li>
              <li>
                <p><a id="detect_DB_LOCK_MAXLOCKS"></a>
                  <code class="literal">DB_LOCK_MAXLOCKS</code>
            </p>
                <p>
                 Reject the lock request for the locker ID with the most locks.
            </p>
              </li>
              <li>
                <p><a id="detect_DB_LOCK_MAXWRITE"></a>
                  <code class="literal">DB_LOCK_MAXWRITE</code>
            </p>
                <p>
                 Reject the lock request for the locker ID with the most write locks.
            </p>
              </li>
              <li>
                <p><a id="detect_DB_LOCK_MINLOCKS"></a>
                  <code class="literal">DB_LOCK_MINLOCKS</code>
            </p>
                <p>
                 Reject the lock request for the locker ID with the fewest locks.
            </p>
              </li>
              <li>
                <p><a id="detect_DB_LOCK_MINWRITE"></a>
                  <code class="literal">DB_LOCK_MINWRITE</code>
            </p>
                <p>
                 Reject the lock request for the locker ID with the fewest write locks.
            </p>
              </li>
              <li>
                <p><a id="detect_DB_LOCK_OLDEST"></a>
                  <code class="literal">DB_LOCK_OLDEST</code>
            </p>
                <p>
                 Reject the lock request for the locker ID with the oldest lock.
            </p>
              </li>
              <li>
                <p><a id="detect_DB_LOCK_RANDOM"></a>
                  <code class="literal">DB_LOCK_RANDOM</code>
            </p>
                <p>
                Reject the lock request for a random locker ID.
            </p>
              </li>
              <li>
                <p><a id="detect_DB_LOCK_YOUNGEST"></a>
                  <code class="literal">DB_LOCK_YOUNGEST</code>
            </p>
                <p>
                 Reject the lock request for the locker ID with the youngest lock.
            </p>
              </li>
            </ul>
          </div>
        </div>
        <div class="sect3" lang="en" xml:lang="en">
          <div class="titlepage">
            <div>
              <div>
                <h4 class="title"><a id="idp8047296"></a>rejected</h4>
              </div>
            </div>
          </div>
          <p>
                          If the <span class="bold"><strong>rejected</strong></span> parameter is
                          non-NULL, the memory location to which it refers will be set to the
                          number of lock requests that were rejected.
                     </p>
        </div>
      </div>
      <div class="sect2" lang="en" xml:lang="en">
        <div class="titlepage">
          <div>
            <div>
              <h3 class="title"><a id="idp8012488"></a>Errors</h3>
            </div>
          </div>
        </div>
        <p>
                         The <code class="methodname">DbEnv::lock_detect()</code> <span>
            
            <span>
                method may fail and throw a <a class="link" href="dbexception.html" title="Chapter 6. The DbException Class">DbException</a> 
                exception, encapsulating one of the following non-zero errors, or return one
                of the following non-zero errors:
            </span>
        </span>
                    </p>
        <div class="sect3" lang="en" xml:lang="en">
          <div class="titlepage">
            <div>
              <div>
                <h4 class="title"><a id="idp8025848"></a>EINVAL</h4>
              </div>
            </div>
          </div>
          <p>
                An invalid flag value or parameter was specified.
            </p>
        </div>
      </div>
      <div class="sect2" lang="en" xml:lang="en">
        <div class="titlepage">
          <div>
            <div>
              <h3 class="title"><a id="idp8040784"></a>Class</h3>
            </div>
          </div>
        </div>
        <p>
                 <a class="link" href="env.html" title="Chapter 5.  The DbEnv Handle">DbEnv</a>, <a class="link" href="lock.html" title="Chapter 7.  The DbLock Handle">DbLock</a> 
            </p>
      </div>
      <div class="sect2" lang="en" xml:lang="en">
        <div class="titlepage">
          <div>
            <div>
              <h3 class="title"><a id="idp8035464"></a>See Also</h3>
            </div>
          </div>
        </div>
        <p>
                     <a class="xref" href="lock.html#locklist" title="Locking Subsystem and Related Methods">Locking Subsystem and Related Methods</a> 
                </p>
      </div>
    </div>
    <div class="navfooter">
      <hr />
      <table width="100%" summary="Navigation footer">
        <tr>
          <td width="40%" align="left"><a accesskey="p" href="envset_lk_tablesize.html">Prev</a> </td>
          <td width="20%" align="center">
            <a accesskey="u" href="lock.html">Up</a>
          </td>
          <td width="40%" align="right"> <a accesskey="n" href="lockget.html">Next</a></td>
        </tr>
        <tr>
          <td width="40%" align="left" valign="top">DbEnv::set_lk_tablesize() </td>
          <td width="20%" align="center">
            <a accesskey="h" href="index.html">Home</a>
          </td>
          <td width="40%" align="right" valign="top"> DbEnv::lock_get()</td>
        </tr>
      </table>
    </div>
  </body>
</html>
